In what is being described as a comprehensive speech, Mr Johnson will tell the European Union he is prepared to accept customs checks at Britain's borders if he cannot secure the sort of trade deal he wants.
One option the PM could support would be a Canada-style free trade deal which allows tariff-free trade for the majority of goods, but would not cover the UK's service industry - which accounts for more than 80% of UK jobs.
Reports in recent days have suggested EU chiefs want the UK to continue to follow Brussels-made rules on standards and state subsidies - while accepting the jurisdiction of the European Court of Justice in any trade disputes.
Speaking to the BBC's Andrew Marr Show, Mr Varadkar said it was possible for the UK to have a "Canada-style agreement".
However he said that if the UK wanted a tariff-free trade deal "then that needs to come with a level playing field" adding "we have very strong views on fair competition and state aid."
A level playing field is a trade policy phrase for a set of common rules and standards that prevent businesses in one country undercutting their rivals and gaining a competitive advantage over those operating in other countries.